In a projection apparatus used in a projector, a mirror having a reflection surface needs to be disposed in the projection apparatus with a high positioning accuracy. Therefore, conventionally, the mirror is fixed onto a fixing member provided in the projection apparatus by means of a number of screws or the like. For this reason, if the mirror expands and contracts due to the change in temperature, humidity or the like, a stress may be originated from a portion fixed by the screw may be accumulated inside the mirror, and the shape of the reflection surface of the mirror may be deformed by the stress. As a result, if there is a change in temperature, humidity or the like, there is a problem that the distortion may occur in an optical image emitted by the projection apparatus, and therefore a large distortion may occur in an output image of the projector.
In order to solve this problem, the following mirror supporting mechanism has been proposed. This mirror supporting mechanism includes a supporting frame formed to locally contact the front surface side of the mirror, a backside member fixed to the supporting frame so that the backside member faces the backside of the mirror with a gap formed therebetween, and a pushing member that pushes the mirror frontward against the backside member. The mirror is slidably sandwiched between the supporting frame and the pushing member, so as to relax the accumulation of stress inside the mirror due to the expansion and contraction of the mirror, and to reduce the deformation of the shape of the reflection surface of the mirror (see for example, Patent Document 1).
Patent Document 1: Japanese Laid-open Patent Publication No. 2003-215713 (paragraph 0018, FIG. 4)